Image registration in a multiple magnification photocopying system

ABSTRACT

A xerographic machine with multiple magnification capabilities employs a multiple focus lens system designed to operate under fixed overall conjugate conditions. The lens system is supported for displacements along its optical axis to effect various magnifications and for displacements perpendicular to the optical axis to regulate the dimensions of the borders on the copies produced by the machine.

United States Patent 1191 Buddendeck et 'al.

1451 Aug. 13, 1974 IMAGE REGISTRATION IN A MULTIPLE MAGNIFICATIONPHOTOCOPYING SYSTEM [75] Inventors: Gerald A. Buddendeck; Herman L.

Cox, both of Rochester, NY.

[73] Assignee: Xerox Corporation, Stamford,

, Conn.

[22] Filed: Jan. 8, I973 [2]] Appl. No; 321,627

' Related US. Application Data I [63] Continuation of Ser. No. 152,134,June 11, 1971,

abandoned.

[52 US. Cl; 355/14, 355/57, 355/66 [51] Int. Cl 15/00 [58] Field ofSearch 355/3, l4, 66, 57; 95/4.5

[56] References Cited UNITED STATES PATENTS 2,160,277 5/1939 Neidich9514.5 1

3,437,410 4/1969 Tregay et al 355/66 X 3,549,254 l2/l970 Muir 355/l4 X3,572,924 3/ 1971 Matsumoto.. 355/57 3,586,437 6/1971 Dietz et al.355/14 3,669,412 6/1972 Ogawa 355/14 X 3,7l6,294 2/1973 Knechtel et al355/14 X Primary Examiner-Samuel S. Matthews Assistant Examiner-RichardA. Wintercorn [57] ABSTRACT A xerographic machine with multiplemagnification capabilities employs a multiple focus lens system designed to operate under fixed overall conjugate conditions. The lenssystem is supported for displacements along its optical axis to effectvarious magnifications and for displacements perpendicular to theoptical .axis to regulate the dimensions of the borders on the copiesproduced by the machine.

'19 Claims, 6Drawing Figures PAIENTEB mm mm INVENTORS. GERALD A.BUDDENDECK HERM x ATTORNEY PATENIEUAUBIBISH 3,3 9, I

swear s I 1 1 f RU PATENTEU M181 31974 3.829.209

FIG. 3

PISTENTED 31974 3.829.209 W550i 5 FIG. 5

.IMAGE REGISTRATIQNIN A MULTIPLE MAGNIFICATION PnorocoPYrNG SYSTEM Thisis a continuation, of application Serial No. 152,134 filed 6/11/71 nowabandoned.

BACKGROUND OF THE INVENTION THis invention relates to photocopyingsystems and in particular to methods and apparatus for regulating thedimensions of the borders on copies made by photocopying systems havingvariable magnification capabilities.

Typically, photocopying systems generate copies by exposing aphotosensitive target to a light image, i.e., electromagnetic radiationin imagewise configuration. The exposure of the photosensitive targetgives rise to a latent image in or on the target that is developed,i.e., rendered visible, simultaneously or subsequently to the exposure.The developed image, while on the target, can comprise the finalproduct'or thedeveloped image may be transferred to atransfer membersuch as ordinary paper. The light image can be generated by a pluralityof means including a cathode ray tube (CRT), light image generatingmeans other than a CRT, illuminating an opaque original or illuminatinga transparent original. I 1

A variable magnification capability can be incorporated into aphotocopying system by using add lens or other variable focus lenssystems designed for fixed overall conjugate environments to project thelight image to the target. Conventionally, the location of the objectand image planes of the lens system are fixed with the light image beingprojected from the object plane to the photosensitive target located atthe image plane. Different magnifications are possible by moving thelens system along the optical axis toward the target to reduce the sizeof the projected light image and by moving the lens system along theoptical axis away from the target to increase the size of the projectedlight image. The add lens and other multiple focus lens systems includeprovisions for maintaining the projected light image in focus when thelens elements are positioned at different locations relative to thetarget.

To maintain a light image centered on the target for a plurality ofdifferent magnifications of the light image, (assuming for the presentthat centering is the desired border regulation), the location of thelight image and/or the target must be adjusted in two dimensions in theobject and image planes of the lens system. For example, the lens systemmay initially be positioned for a 1:1 projection of a light imagemovable in the object plane to a target fixed in the image plane. Toproject a larger size light image to the same target so the larger imageis confined to the area on the target occupied by the image in the 1:1case, the lens system is moved along the optical axis toward the target.to effect the necessary image reduction, (automatic focus is assumed).In addition, the larger light image must be positioned over the originalimage in a concentric fashion with balanced amounts of overlap on allsides, i.e., the larger image must be centered over the smaller by somemachine or hand operation. If the centering operation is not followed,portions of the projected light image will fall outside the target arearesulting in partial loss of the image or at least creation ofnon-symmetrical borders around the final copy. This example illustratesone drawback of photocopying systems designed to reduce large documentsto a single convenient size. An analogous drawback is associated withsystems designed for image enlargement wherein a light image such as amicro image is blown up to different sizes. The drawback lies with themultiple directional manipulation of the light image and/or the targetin order to prevent image loss and/or to regulate the dimensions of theborders in the final copy. The multiple direction manipulations areundesirable because it complicates the photocopying system design.

Accordingly, it is anobject of this invention to overcome the abovenoted drawback and other similar problems encountered by prior artphotocopying systems capable of two or more magnifications.

Specifically, it is an object of the present invention for imagealignment purposes to limit target and/or light image manipulation inphotocopying machines to movements along a single coordinate.

Yet another object of this invention is to enhance the performance ofadd lens and other multiple focus lens systems by introducing lenselement displacements away from an optical axis in addition to lensdisplacements along the optical axis.

Still another object of the instant invention is to regulate thedimensions of copy borders for photocopying machines of the type whereinthe photosensitive target travels through the lens system image plane bydisplacing the image forming area of the target by electrically delayingor accelerating the start of the image forming process.

Another object of this invention is to devise method and apparatus forregulating borders in a xerographic photocopying machine employing flashor instantaneous exposure of a planar surface of an electricallyphotosensitive target in web form.

Even another object of this invention is to design an exposure mechanismfor a photocopying machine wherein different size documents areprojected to a fixed target area in registration by simply aligning oneedge of any size document against a linear registration guide.

Another object of this invention is to device reliable and economicmethods and apparatus for the displacement of multiple focus lenssystems relative to the optical axis of the lens systems.

These and other objects of the present invention are realized byemploying novel photocopying methods and apparatus for projectingvarious size light images to a single size photosensitive target. Onetechnique includes displacing a projection lens system perpendicular toits optical axis in addition to along the optical axis. Anothertechnique includes delaying or accelerating the instant in time at whichimage formation takes place. Both techniques permit multiple size lightimages to be projected and reduced or enlarged to the same target areawhile requiring the light image (and- /or the target) to be movedalongone rather than two coordinates.

DESCRIPTION OF THE DRAWINGS Other objects and features of the instantinvention will be apparent from the present description and from thedrawings which are:

FIG. 1 is a side view in partial cut-away of a xerographicphotocopyingmachine having a multiple magnification capability in whichthe present invention is employed.

FIG. 2 is a perspective view of the exposure mechanism used in themachine in FIG. 1.

FIG. 3 is a simplified schematic of the optical path of the apparatus inFIG. Zunfolded into a generally linear path by eliminating the planemirrors in FIG. 2.

FIG. 4 is a side elevation view of apparatus for effecting displacementof an add lens system along and away from the initial optical axis.

FIG. 5 is a plan view of the apparatus of FIG. 4.

FIG. 6 is a partial elevation view of the apparatus of FIG. 4. as viewedfrom the side-opposite to that in FIG. 4. illustrating the cam forinserting an add lens into the lens system.

DESCRIPTION OF THE EMBODIMENTS The following description of thisinvention is in terms of a xerographic photocopying machine thatprovides l:l magnification and image reduction. It is to be understoodthat the methods and apparatus disclosed may be readily adapted to amachine havingan image enlargement capability and to photocopyingmachines utilizing electrical, magnetic, chemical, heat and/or otherimage forming processes.

The xerographic photocopying machine 1 of FIG. 1.

includes the electrically photosensitive target 2 that is in the form ofa continuous web or belt. The belt 2 is appropriately supported fortravel in a rotary fashion around the rollers 3, 4 and 5. The outsidesurface of the belt has electrostatic charge continuously deposited ontoit as it passes the charging corotron 8. The charged belt is exposed toa light image between rollers 3 and 4 as indicated roughly by the lightrays 9and l0 projected by the exposure mechanism 11. The light altersthe electrostatic charge on the photosensitive belt giving rise to alatent electrostatic image. The latent electrostatic image is developedas the belt travels past the developing apparatus 12 which includes aplurality of magnetic brush developer rollers 13. The developingapparatus presents electrically charged marking or toner particlesadjacent the latent image which are electrically attracted to the beltin imagewise configuration yielding a developed or visible toner image.The toner image is transferred from the belt to a transfer member (e.g.,ordinary paper) fed to the belt in registration with the toner image.

A transfer member is transported to the belt 2 by an appropriate meansincluding the transport mechanism 14. The transfer of the toner imagetakes place when the transfer member and belt pass the electricallybiased transfer roller 15. The toner image on the transfer memberiscarried by the conveyor 16 to a suitable fusing mechanism 17 where thetoner image is pennanently fixed to the transfer member. The fixed tonerimage is the final product or copy which is collected in the output tray18.

The belt area on which the foregoing toner image is formed isreconditioned for formation of another image by the preclean chargingcorotron 22 and the cleaning device 23. Device 23 includes a rotarybrush 25 surrounded by a housing 24 which is connected to a vacuumsource. The belt thereafter returns to its starting position underneaththe charging corotron 8 which prepares thebelt for formation of a newtoner image.

Machine 1 is capable of forming copies on different size transfermembers which are supplied to the belt over two different transportpaths 'partially definedby transport mechanisms 26 and 27.

The specific charging, developing, transferring, fusing and transportingmechanisms disclosed in the drawings and described herein are explainedin greater detail in copending applications entitled ControllingMultiple Voltage Levels for Electrostatic Printing in the name ofFeldeisen et-al., Ser. No. 152,138, and Corotron Structure forElectrostatic Machines" in the name of Daniel L. Mueller, Ser. No.152,137 both filed currently herewith and the U.S. Pat. No. 3,661,452 inthe name of Hewes et al. The disclosures of these copending applicationsare incorporated herein by reference. For other descriptions ofxerographic process steps see U.S. Pat. Nos. 3,062,109 and 3,301,126 andthe patents mentioned therein which are also incorporated herein byreference.

The projection or exposure mechanism 11 with which the present inventionis primarily concerned is comprised of the platen 30 which holds theopaque originals or documents that are copied. The platen is uniformlyflooded with electromagnetic radiation generated by the lamps 31 and32'and directed to the platen by the mirror reflectors 33 and 34. Thelight reflected off a document on the platen comprises the light imagetowhich the belt 2 is exposed. This light image is projected to the beltby the lens system 37 and plane mirrors 38 and 39. Y

The duration of the exposure, i.e., the length of time the lamps 31 and32 generate radiation, is such that the belt 2 can be assumed stationaryduring the exposure period. Consequently, the location of an image onthe belt is controlled by accelerating or delaying the instant at whichthe lamps are turned on, i.e., flashed. The acceleration or delay of theflash exposure is conveniently provided by electrical circuitry known tothose skilled in the art since the lamps are electrically operatedillumination sources. The moment of flash is determined by timing meansoperated in conjunction with the cyclic travel of the belt aroundrollers 3, 4, and 5.

FIG. 2, depicts the exposure mechanism of the presently discussedembodiment which includes the platen 30, linear registration guide 40,the different size documents 41 and 42, plane mirrors 38 and 39, thelens system 37 and the plane surface of belt 2 between rollers 3 and 4.The registration guide includes a calibrated straight edge having meanssuch as a mark 45 for registering one dimension of a document to thebelt 2. The alignment of a document to the registration guideestablishes the location of the latent electrostatic image on belt 2between the lateral boundaries of the belt conveniently represented bythe imaginary registration marks 46 and 47. The location of the latentimage between the imaginary registration marks 47 and 48 is establishedby alignment of the optical axis of the lens system 37 relative to adocument and the target.

As mentioned earlier, the belt surface area on which the latentelectrostatic image is formed can be varied by accelerating or delayingthe flash of the exposure lamps. This variation to the flash ultimatelyshifts the toner image on the transfer member because the belt speed andthe instant in time at which the belt intercepts the transfer member arefixed.

The coordinate defined by a line between imaginary marks 47 and 48 isparallel to the coordinate 50 if the effect of mirrors 38 and 39 isignored. Coordinate 50 is the dimension of the latent image in which aregistration change will occur when different size documents are alignedto the registration guide 40. The cross marks 51 and 52 represent thegeometric center of two arbitrarily selected documents 41. and 42,respectively. These geometric centers lie on line 50 because one edge ofeach document is centered (assuming for the present that centeringdefines the desired border condition) to mark 45 on the registrationguide. This means that when the lens system 37 is displaced along theoptical axis to change the magnification, the location of the projectedimage relative to the imaginary marks 47 and 48 changes. The shift inlatent image location causes a copy of document 41 to have differentborder dimensions than a copy of document 42. One goal of this inventionis to make the borders on both copies substantially the same or at leastsymmetrical.

FIG. 3 is helpful in understanding the above registration problem andthe present solution of the problem. The drawing is a simplifiedschematic of a ray trace for the lens system of FIG. 2. with the mirrors38 and 39 removed. The schematic illustrates edges of documents 41 and42 that are parallel to line 50 in FIG. 2 and the edge of belt 2parallel to a line between imaginary marks 47 and 48. The lens system 37is shown as a single lens element with the solid lines 37 representingthe lens position for a 1:1 projection of document 41 to a positionbetween imaginary marks 47 and 48v and the dashed lines 37a representingthe lens system position for projecting the larger document 42 to thesame location between marks 47 and 48.

Prior art add lens systems called for the positioning of the lens system37 at locations broadly defined by points X and Y for projection ofdifferent size documents such as documents 41 and 42.-Point X is thelocation for a 1:1 magnification and point Y is the location for animage reduction. The image of document 41 projected with the lens atpoint X completely fills the area between marks 47 and 48 as indicatedby rays 58 and 59 which is assumed for present purposes to be acondition yielding copies with no borders. The image of document 42projected with the lens at point Y fills less than all the area betweenmarks 47 and 48 as indicated by the rays 60 and 61. This means the copymade of document 41 has no border and the copy of document 42 has asingle or non-symmetrical border along the edge that was adjacent mark47.

The present inventors overcame the foregoing problem by discovering thatthe image of document 42 can be made to fill the entire area betweenmarks 47 and 48 as indicated by rays 59 and 61 by positioning the lensat point Z. The usefullness of point Z is not readily apparent becauseadd lens and other multiple focus lens systems heretofore have alwaysdescribed lens element displacements as being along a fixed opticalaxis. Point Z, of course, is displaced perpendicularly from the opticalaxis 55 by the amount A which is contrary to prior systems. The newoptical axis is parallel to axis It is within the scope of thisinvention to move-the lens element to point M displaced upward frompointY by an amount 19C where C is the border width produced by positioningthe lens at point Y. With the lens at point M the border on the copy ofdocument 42 is not identical to thaw the copy of document 41 but atleast the copy has symmetrical borders, i.e. borders of k C at each end.

The unique point 2 at which copies of different size documents havesubstantially the same borders at ends adjacent marks 47 and 48 isdefined by the intersection of the extreme rays drawn between oppositeends of a document and the target, e.g. rays 59 and .61. (In thisregard, the distance between imaginary registration points 47 and 48 canvary if different magnifications are desired. Fixed registration marksare illustrated and discussed to help explain the principals of thepresent invention but the invention is not intended to be limited tothat condition.)

An infinite number of points M at which symmetrical borders are yieldedfor copies of document 42 lie along line 63 drawn between the center 52of the document and the center 64 of the target. The lens is moved alongoptical axis 55 to obtain the desired magnification and then displacedupward to line 63 to achieve the symmetrical border condition. (Notethat point Z is a special case of a point M.)

FIGS. 4, 5 and 6 illustrate a displacement mechanism 1.01 for effectingthe on-axis and off-axis displacements of an add lens system.Mechanism101 includes a frame 102, inclined rails 103 and 104, drive unit 105,carriage 106 that carries the main lens element 107 and an add lenselement 108 and a cam unit 109. The lens elements 107 (that is theelements housed inside the barrel) and the add lens elements comprise anadd lens system designated by reference number 37 in FIGS. 1, 2 and 3.For a full descriptionof add lens systems see US. Pat. No. 3,476,478.The disclosure of that patent is incorporated herein by reference. Theframe 102 is supported in machine 1 between mirrors 38 and 39 withbottom surface 114 parallel to an optical axis such as axis 55 in FIG.3. The linear rails 103- and 104 are sloped or inclined relative tosurface 114 to position the lens elements 107 and 108 (as needed)between points corresponding to points X and Z (or M) illustrated inFIG. 3.

The rails 103 and 104 are appropriately supported by the frame 102. Thecarriage 106 is slidably mounted on the rails at four places by suitablebearings 115. The carriage is propelled back and forth along the railsby thedrive unit 105. The drive unit includes a suitable electric motor116 supported by the frame and having the pinion. gear 117 coupled toits drive shaft. The pinion gear is mated with the rack gear 1 l8rigidly coupled to the carriage 106. The pinion and rack gears areoriented in the plane of the rails as best seen in FIG. 4. The motor isreversable and the pinion. gear is rotated clockwise andcounterclockwise to propel the carriage back and forth along the rails.Appropriate contact switches secured to the frame are tripped by thecar- 1 riage to stop the motor when a desired rail position is reached.

The cam unit 109 includes the cam plate 121 rigidly coupled to the'framehaving the arc or cam surface 122 cut therein. The cam follower 123 isrigidly coupled to brace 124 which in turn is pivotally journalled tothe carriage 106. The add lens 108 is supported in the brace.Consequently, the add lens is positioned as shown in FIGS. 4, 5 and 6when the carriage is near the end of the rails closest to the bottomframe surface 1 14. This position of the brace centers the add lens 108about the optical axis of the main lens 107. When the carriage travelstoward the opposite ends of the rails, the cam follower forces the bracedownward as it travels the cam surface. At some point along the railsthe ,7 addlens 108 isremoved from the optical path of the main'l'ens107.}

"The length of the rails may be extended to permit more add lenselements to be used. Also, an add lens is not necessary to everyposition along the rails. Accordingly, the photocopying machine canposition the lens system at several different positions along the railsto achieve equal numbers of different magnifications. The Z points or Mpoints for asystem using more than two magnifications may not fall in astraight line. A non-linear rail path can be provided in this case.Alternately, errosrs in the location of Z and M points caused by thelinear rails can be offset by using the earlier described technique ofdelaying or accelerating the flash exposure to shift the location oflatent image an appropriate amount on the belt 2.

As mentioned at the outset, this invention is not intended to be limitedto the specific embodiments shown but to include those inventionslogically suggested by the present disclosure.

What is claimed is:

1. Exposure apparatus for regulating borders on copies produced by aphotocopying machine capable of generating a light image for exposingaphotosensitive target comprising a single multiple focus lens system forfixed overall conjugate projections positioned relative to said lightimage and target such that the light image is in the object plane of thelens systemand the target is in the image plane of the lens system,

a photosensitive target including a photosensitive member in web formwith a plane surface thereof supported for movement through the imageplane of said lens system,

means for generating said light image including flash lamp meanspositioned to illuminate a platen for supporting an opaque documentwherein said lamp illuminates said platen for a period of timesufficiently short to permit the target to be considered substantiallystationary during exposure,

electrical means for controlling the instant in time at which said flashlamp illuminates the platen for regulating the dimensions of bordersassociated with the copies produced by the machine, and

displacement means for supporting said lens system and for displacingthe lens system parallel to the optical axis to obtain different sizefocused projections of said light images on the target and fordisplacing the lens system perpendicular to the optical axis to regulatethe dimensions of borders associated with copies produced by themachine.

2. The apparatus of claim 1 further including registration meanspositioned in said image plane for aligning one edge of said light imagerelative to said target.

3. The apparatus of claim 1 wherein said lens system includes an addlens system comprising main lens elements and at least one add lenselement.

4. The apparatus of claim 3 further including at least one plane mirrorfor folding the optical path of the lens system without changing theoverall conjugate.

5. The apparatus of claim 4 including two plane mirrors for folding theoptical path of said lens system without changing the overall conjugate.

6. The apparatus of claim 1 wherein said photosensitive target includesan electrically photosensitive memher on which. a latent electrostaticimage is formed upon exposure of the target to the light'image.

7. The apparatus of claim 6 wherein said photocopy ing machine is axerographic machine including means for developing said latentelectrostatic image forming a toner image, means for transferring saidtoner image to a transfer member and means for fixing said toner imagepermanently to the transfer member.

8. The apparatus of claim 7 wherein said photosensitive target includesreusable surface areas and said xerograph'ic machine further includesmeans for cleaning said'target after the toner image is transferredthere from.

9. The apparatus of claim 1 wherein said displacement means includesmeans for positioning said lens system to at least points X and Z whereX is a first lens system position for projecting a focused image of afirst light image to the target and Z is a second lens system positionfor projecting a focused image of a larger light image to the targetwhere Z is defined by the intersection of extreme rays projected fromthe larger light image to the boundaries of the target.

10.'The apparatus of claim 1 wherein said displacement means includesmeans for positioning said lens system'to at least points X and M whereX is a first lens system position for projecting a focused image of afirst light image to the target and M is a second lens system positionfor projecting a focused image of a larger light image to the targetwhere M is definedby the intersectionof a line drawn from the center ofthe larger light image to the center of the target and a line normal tothe optical axis.

11. The apparatus of claim 9 wherein said displacement means includesmeans coupled to said lens system and slidably coupled to at least onelinear rail oriented substantially parallel to a line drawn betweenpoints X and Z.

12. The apparatus of claim 10 wherein said displacement means includesmeans coupled to said lens system and slidably coupled to at least onelinear rail oriented substantially parallel to a line drawn betweenpoints X and M.

13. The apparatus of claim 12 wherein said displacement means includesmeans to position said lens system at point X and a plurality of pointMs with said rail oriented parallel to the line drawn between point Xand the M point furthest from the X point.

14. Exposure apparatus for regulating borders on copies produced by aphotocopying machine comprisa photosensitive target including a planesurface image forming area capable of having a latent electrostaticimage created thereon upon exposure to a light image,

means for generating in a fixedly located plane light images of morethan one size with one edge of all sizes of light images being alignedrelative to one edge of the image forming area of the target forregulating the borders on two opposite sides of said copies,

a multiple focus lens system including means for changing focal lengthto project light images of different size to the target without anyprojected image substantially exceeding the dimensions of the imageforming area upon moving the lens system parallel to the optical axisbut without changing the length of the overall conjugate anddisplacement means for moving said lens system along a linear pathangled to the optical axis defined by points X and M where X is a lenssystem position for projecting a light image of first size to the targetwith the optical axis coincident with a line between the centers of thelight image and target and where M is the intersection of a line betweenthe centers of the target and a light image of second size and a normalfrom point Y on the X position optical axis where Y is the lens systemposition for projecting a light image of a second size to the targetsaid M lens system position causing the production of copies havingborders differing from those resulting from the X lens system positionbut which are nonetheless symmetrical'on opposite sides of the copies.l5. Exposure apparatus for regulating borders on copies produced byaphotocopying machine comprising a photosensitive target including aplane surface image forming area capable of having a latent electrstaticimage formed thereon upon exposure to a light image, means forgenerating in a fixedly located plane light images of at least threesizes being equal to or greater than the image forming area of thetarget with one edge of all sizes of light images being aligned relativeto one edge of the image forming area on the target for regulating theborders on'opposite sides of said copies, multiple focus lens systemincluding means for changing the focal length for the projection of atleast said three light images to the target without any projected imagesubstantially exceeding the dimensions of the image forming area uponmoving the lens system along the optical axis but without changing thelength of the overall conjugate and displacement means for moving saidlens system to at least three positions along a linear path at an angleto the optical axis defined by points X and M where X is a lens systemposition for projecting a light image of first size to the target withthe optical axis coincident with a line between the centers of the lightimage and target and where M is the intersection of a line between thecenters of the target and a light image of a second larger size and anormal from point Y on the X position optical axis where Y is the lenssystem position for projecting said light image of second size to thetarget, said third lens system position on said linear path notincluding the point of intersection between the line between the centersof the target and a light image of third size and a normal from point Yon the X position optical axis where Y is the lens system position forprojecting said light image of said third size to the target.

16. The apparatus of claim 15 wherein said target is supported formovement through the image plane of said lens system, said means forgenerating light images includes flash lamp means for illuminating aplaten for supporting opaque documents, said period of illuminationbeing a time sufficiently short compared to the rate of travel of thetarget to enable the target to be considered stationary during theexposure and further including electrical circuit means for controllingthe instant in time the illumination occurs in order to regulate theborders associated with copies produced when said lens system ispositioned at said third lens system position.

17. An electrostatic reproduction maching having an illumination meanswherein copies of an original document are produced by flashing theillumination means to produce a flashed light image onto a photoreceptorand effect an electrostaticlatent image thereon disposed in an imageplane, including,

lens means for projecting a flashed light image of said originaldocument onto said photoreceptor, means for producing a flash exposureof the document in timed relation with the movement of thephotoreceptor, and

flash control means coupled to said producing means for effecting flashenergizing of the illumination means to generate a flashed light image,said flash control means being responsive to a selectable means forvarying the application of said flash energization of said illuminationmeans for a predetermined time duration thereby shifting the formationof an electrostatic latent image on the photoreceptor relative to itsmachine-timed position without the varying of flash exposure.

18. Tl-le machine of claim 17 wherein said varying of the application offlash energization is such as to delay flash exposure.

19. An electrostatic reproduction machine having an illumination meansfor. producing electrostatic latent images upon a moving photoreceptorweb thereon; developing apparatus for developing the latent images;sheet feed means for feeding sheets seriatim to the developed images;transfer means for effecting the transfer of developed images to sheets;and machine control means for (a) flashing the illumination means, (b)for activating the sheet feed means and (c) the transfer means in timedrelation to the moving photoreceptor web, the improvement includingflash control means coupled to the machine control means beingresponsive to a selectable means for delaying the application of theflashing of the illumination means while maintaining the timedrelationship for the activation of the sheet feed means.

1F i i

1. Exposure apparatus for regulating borders on copies produced by aphotocopying machine capable of generating a light image for exposing aphotosensitive target comprising a single multiple focus lens system forfixed overall conjugate projections positioned relative to said lightimage and target such that the light image is in the object plane of thelens system and the target is in the image plane of the lens system, aphotosensitive target including a photosensitive member in web form witha plane surface thereof supported for movement through the image planeof said lens system, means for generating said light image includingflash lamp means positioned to illuminate a platen for supporting anopaque document wherein said lamp illuminates said platen for a periodof time sufficiently short to permit the target to be consideredsubstantially stationary during exposure, electrical means forcontrolling the instant in time at which said flash lamp illuminates theplaten for regulating the dimensions of borders associated with thecopies produced by the machine, and displacement means for supportingsaid lens system and for displacing the lens system parallel to theoptical axis to obtain different size focused projections of said lightimages on the target and for displacing the lens system perpendiculAr tothe optical axis to regulate the dimensions of borders associated withcopies produced by the machine.
 2. The apparatus of claim 1 furtherincluding registration means positioned in said image plane for aligningone edge of said light image relative to said target.
 3. The apparatusof claim 1 wherein said lens system includes an add lens systemcomprising main lens elements and at least one add lens element.
 4. Theapparatus of claim 3 further including at least one plane mirror forfolding the optical path of the lens system without changing the overallconjugate.
 5. The apparatus of claim 4 including two plane mirrors forfolding the optical path of said lens system without changing theoverall conjugate.
 6. The apparatus of claim 1 wherein saidphotosensitive target includes an electrically photosensitive member onwhich a latent electrostatic image is formed upon exposure of the targetto the light image.
 7. The apparatus of claim 6 wherein saidphotocopying machine is a xerographic machine including means fordeveloping said latent electrostatic image forming a toner image, meansfor transferring said toner image to a transfer member and means forfixing said toner image permanently to the transfer member.
 8. Theapparatus of claim 7 wherein said photosensitive target includesreusable surface areas and said xerographic machine further includesmeans for cleaning said target after the toner image is transferredtherefrom.
 9. The apparatus of claim 1 wherein said displacement meansincludes means for positioning said lens system to at least points X andZ where X is a first lens system position for projecting a focused imageof a first light image to the target and Z is a second lens systemposition for projecting a focused image of a larger light image to thetarget where Z is defined by the intersection of extreme rays projectedfrom the larger light image to the boundaries of the target.
 10. Theapparatus of claim 1 wherein said displacement means includes means forpositioning said lens system to at least points X and M where X is afirst lens system position for projecting a focused image of a firstlight image to the target and M is a second lens system position forprojecting a focused image of a larger light image to the target where Mis defined by the intersection of a line drawn from the center of thelarger light image to the center of the target and a line normal to theoptical axis.
 11. The apparatus of claim 9 wherein said displacementmeans includes means coupled to said lens system and slidably coupled toat least one linear rail oriented substantially parallel to a line drawnbetween points X and Z.
 12. The apparatus of claim 10 wherein saiddisplacement means includes means coupled to said lens system andslidably coupled to at least one linear rail oriented substantiallyparallel to a line drawn between points X and M.
 13. The apparatus ofclaim 12 wherein said displacement means includes means to position saidlens system at point X and a plurality of point M''s with said railoriented parallel to the line drawn between point X and the M pointfurthest from the X point.
 14. Exposure apparatus for regulating borderson copies produced by a photocopying machine comprising a photosensitivetarget including a plane surface image forming area capable of having alatent electrostatic image created thereon upon exposure to a lightimage, means for generating in a fixedly located plane light images ofmore than one size with one edge of all sizes of light images beingaligned relative to one edge of the image forming area of the target forregulating the borders on two opposite sides of said copies, a multiplefocus lens system including means for changing focal length to projectlight images of different size to the target without any projected imagesubstantially exceeding the dimensions of the image forming area uponmoving the lens system parallel to the optical axis but without changingthe length of the overall conjugate and displacement means for movingsaid lens system along a linear path angled to the optical axis definedby points X and M where X is a lens system position for projecting alight image of first size to the target with the optical axis coincidentwith a line between the centers of the light image and target and whereM is the intersection of a line between the centers of the target and alight image of second size and a normal from point Y on the X positionoptical axis where Y is the lens system position for projecting a lightimage of a second size to the target said M lens system position causingthe production of copies having borders differing from those resultingfrom the X lens system position but which are nonetheless symmetrical onopposite sides of the copies.
 15. Exposure apparatus for regulatingborders on copies produced by a photocopying machine comprising aphotosensitive target including a plane surface image forming areacapable of having a latent electrstatic image formed thereon uponexposure to a light image, means for generating in a fixedly locatedplane light images of at least three sizes being equal to or greaterthan the image forming area of the target with one edge of all sizes oflight images being aligned relative to one edge of the image formingarea on the target for regulating the borders on opposite sides of saidcopies, a multiple focus lens system including means for changing thefocal length for the projection of at least said three light images tothe target without any projected image substantially exceeding thedimensions of the image forming area upon moving the lens system alongthe optical axis but without changing the length of the overallconjugate and displacement means for moving said lens system to at leastthree positions along a linear path at an angle to the optical axisdefined by points X and M where X is a lens system position forprojecting a light image of first size to the target with the opticalaxis coincident with a line between the centers of the light image andtarget and where M is the intersection of a line between the centers ofthe target and a light image of a second larger size and a normal frompoint Y on the X position optical axis where Y is the lens systemposition for projecting said light image of second size to the target,said third lens system position on said linear path not including thepoint of intersection between the line between the centers of the targetand a light image of third size and a normal from point Y on the Xposition optical axis where Y is the lens system position for projectingsaid light image of said third size to the target.
 16. The apparatus ofclaim 15 wherein said target is supported for movement through the imageplane of said lens system, said means for generating light imagesincludes flash lamp means for illuminating a platen for supportingopaque documents, said period of illumination being a time sufficientlyshort compared to the rate of travel of the target to enable the targetto be considered stationary during the exposure and further includingelectrical circuit means for controlling the instant in time theillumination occurs in order to regulate the borders associated withcopies produced when said lens system is positioned at said third lenssystem position.
 17. An electrostatic reproduction maching having anillumination means wherein copies of an original document are producedby flashing the illumination means to produce a flashed light image ontoa photoreceptor and effect an electrostatic latent image thereondisposed in an image plane, including, lens means for projecting aflashed light image of said original document onto said photoreceptor,means for producing a flash exposure of the document in timed relationwith the movement of the photoreceptor, and flash control Means coupledto said producing means for effecting flash energizing of theillumination means to generate a flashed light image, said flash controlmeans being responsive to a selectable means for varying the applicationof said flash energization of said illumination means for apredetermined time duration thereby shifting the formation of anelectrostatic latent image on the photoreceptor relative to itsmachine-timed position without the varying of flash exposure.
 18. THemachine of claim 17 wherein said varying of the application of flashenergization is such as to delay flash exposure.
 19. An electrostaticreproduction machine having an illumination means for producingelectrostatic latent images upon a moving photoreceptor web thereon;developing apparatus for developing the latent images; sheet feed meansfor feeding sheets seriatim to the developed images; transfer means foreffecting the transfer of developed images to sheets; and machinecontrol means for (a) flashing the illumination means, (b) foractivating the sheet feed means and (c) the transfer means in timedrelation to the moving photoreceptor web, the improvement includingflash control means coupled to the machine control means beingresponsive to a selectable means for delaying the application of theflashing of the illumination means while maintaining the timedrelationship for the activation of the sheet feed means.